New Delhi: Intelligence agencies have alerted the Bureau of Civil aviation security (BCAS) about a likely hijack attempt on an Air India flight.

Sensitive airports around the country and Kabul have been alerted. Reports suggest that the Delhi-Kabul flight could be targeted.

"Security around all the airports have been strengthened and we have taken all the measures that are required in the wake of the alert from intelligence agencies," official sources said on Sunday.

All anti-hijacking measures have been put in place, they said, adding that passengers' checking has also been beefed up at some of the major airports, including Indira Gandhi International Airport here.

The airport staff has been asked to carry out checking of the cabin baggage once the boarding is competed and even the airport staff is being thoroughly checked by the airport security personnel, they said.

US President Barack Obama is scheduled to visit India this month to attend the Republic Day celebrations as the chief guest.

Security expert Qamar Agha on Sunday termed the hijack threat  as 'very serious' and hoped that the government will take it seriously as Kolkata is on the target list of Pakistan backed extremists.

"This is a very serious matter and I am sure government must be taking it very seriously. Kolkata has been targeted for quite some time, it is on the hit list for a long time. Bengal is one state, which is very close to Bangladesh. We all know Pakistan has ISI backed organizations which are operating, they have created strategic assets over there," he told ANI.

"In Bengal, Assam and in some southern states of India they have created their sleeper cells. So, therefore, the warning has become very serious," he added.

A threat phone call was made to the Air India office in Kolkata last evening and a complaint was lodged with the police. The security at the Kolkata airport has been increased after the threat call.